From 1a534c7f1e2cf672bbdd800e229cfe34eb089cc5 Mon Sep 17 00:00:00 2001
From: Reimar Döffinger <Reimar.Doeffinger@gmx.de>
Date: Tue, 3 Feb 2009 14:20:55 +0000
Subject: Add and use a public API for RC4 and DES, analogous to the AES API.

Originally committed as revision 16970 to svn://svn.ffmpeg.org/ffmpeg/trunk
---
 libavutil/rc4.c | 35 ++++++++++++++++++++++++++++-------
 1 file changed, 28 insertions(+), 7 deletions(-)

(limited to 'libavutil/rc4.c')

diff --git a/libavutil/rc4.c b/libavutil/rc4.c
index 0cf71a4194..e6e7dc9e1a 100644
--- a/libavutil/rc4.c
+++ b/libavutil/rc4.c
@@ -20,13 +20,19 @@
  * License along with FFmpeg; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
+#include "avutil.h"
 #include "common.h"
 #include "rc4.h"
 
-void ff_rc4_enc(const uint8_t *key, int keylen, uint8_t *data, int datalen) {
+typedef struct AVRC4 AVRC4;
+
+int av_rc4_init(AVRC4 *r, const uint8_t *key, int key_bits, int decrypt) {
     int i, j;
-    uint8_t x, y;
-    uint8_t state[256];
+    uint8_t y;
+    uint8_t *state = r->state;
+    int keylen = key_bits >> 3;
+    if (key_bits & 7)
+        return -1;
     for (i = 0; i < 256; i++)
         state[i] = i;
     y = 0;
@@ -36,13 +42,28 @@ void ff_rc4_enc(const uint8_t *key, int keylen, uint8_t *data, int datalen) {
         y += state[i] + key[j];
         FFSWAP(uint8_t, state[i], state[y]);
     }
-    // state initialized, now do the real encryption
-    x = 1; y = state[1];
-    while (datalen-- > 0) {
+    r->x = 1;
+    r->y = state[1];
+    return 0;
+}
+
+void av_rc4_crypt(AVRC4 *r, uint8_t *dst, const uint8_t *src, int count, uint8_t *iv, int decrypt) {
+    uint8_t x = r->x, y = r->y;
+    uint8_t *state = r->state;
+    while (count-- > 0) {
         uint8_t sum = state[x] + state[y];
         FFSWAP(uint8_t, state[x], state[y]);
-        *data++ ^= state[sum];
+        *dst++ = src ? *src++ ^ state[sum] : state[sum];
         x++;
         y += state[x];
     }
+    r->x = x; r->y = y;
+}
+
+#if LIBAVUTIL_VERSION_MAJOR < 50
+void ff_rc4_enc(const uint8_t *key, int keylen, uint8_t *data, int datalen) {
+    AVRC4 r;
+    av_rc4_init(&r, key, keylen * 8, 0);
+    av_rc4_crypt(&r, data, data, datalen, NULL, 0);
 }
+#endif
-- 
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